Memory Sub-System Touch-Up for Charge Loss
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Solution Overview
Problem
Non-volatile memory devices, such as NAND flash memory, face data retention issues due to charge loss, leading to potential data loss and increased resource consumption for error correction and data transfer, which affects system performance and endurance.
Innovation Solution
Implementing a touch-up operation that uses a NAND copy back read and write operation to reprogram memory cells with charge loss, eliminating the need for data transfer on a data bus and reducing resource overhead by directly addressing charge loss on target pages rather than moving data to new locations, thereby avoiding error correction and system controller involvement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If data is transferred to new locations for error correction, then data integrity is maintained, but system performance and endurance deteriorate due to increased resource consumption
Solution Approach 1:
The patent extracts and addresses only the specific memory cells with charge loss (below threshold voltage) rather than transferring all data. The touch-up operation selectively reprograms only the affected cells in place, eliminating the need for complete data transfer and error correction procedures, thus maintaining data integrity while preserving system performance
Solution Approach 2:
The patent uses a copyback read operation to read data from the target page and then performs a copyback program to write it back, during which the touch-up operation reprograms affected cells. This copying mechanism allows in-place correction without requiring data movement to alternative locations, reducing resource overhead while ensuring data integrity
2Reliability
If background scans and error correction are performed, then charge loss is detected and corrected, but resource overhead increases
Solution Approach 1:
The patent performs the touch-up operation during the copyback program phase, which is a preliminary action that occurs before normal read operations would detect errors. By proactively reprogramming cells during the write-back process, the system prevents charge loss from escalating to detectable errors, eliminating the need for subsequent background scans and error correction procedures
Solution Approach 2:
The touch-up operation is integrated into the existing copyback read and write operations, allowing the memory subsystem to self-correct charge loss without requiring separate error correction mechanisms. The system uses its own operational cycles (read/write) to simultaneously perform data transfer and charge loss correction, reducing overall resource overhead
Data Source
AI summary
An apparatus can include a touch-up component. The touch-up component can detect that at least one memory cell of a page of memory cells has lost a portion of a charge. The touch-up component can set touch-up parameters for the page of memory cells. The touch-up component can cause a transfer of data from the page of memory cells to a cache. The touch-up component can reprogram the at least one memory cell using the set touch-up parameters.